The invention relates to an exchanger element for bottoms in material exchanger columns, comprising a cylinder fastened vertically in bottom openings, provided with grid openings for the passage of the gas, with a stationary cover plate for the deflection of the gas, and an inner mobile valve plate, one or several apertures for the widening of the counter-current process, such as rectification, absorption, desorption, gas cooling, gas saturation, etc., which are carried out in so-called columns, and in which the necessary intimate contact between the flowing gas and liquid phases is caused by exchanger bottoms.
These exchanger bottoms essentially consist of apertures (holes) for the gas passage and the so-called liquid shafts for the inlet and/or outlet of the liquid on the bottom.
The so-called screen bottom is the simplest exchanger bottom of this kind. The ascending gas penetrates through perforations in the horizontally arranged bottom panel and through the liquid flowing above the bottom, whereby an exchange of material and heat takes place. The load range of such a screen bottom is limited because already at a slight decrease of the gas load for which gas passage cross-sections were calculated hydraulically, the liquid escapes through the gas passage aperture as a result of the static superpressure, and as a result thereof, the effectiveness of the bottom decreases considerably.
The direct vertical passage of the gas through the liquid is another disadvantage of this exchanger bottom in case of screen bottoms.
So-called valve bottoms are known preponderantly as exchanger bottoms; essentially they consist of circular or oblong covering devices located on apertures in the bottom panel and guided by guide arms which protrude into the bottom aperture and/or are fastened above the bottom panel. In addition to the known mechanical disadvantages, such as considerable wear of the guide arms and/or enlargement of the bottom aperture due to erosion, the capability of adapting to the required maximum and minimum gas loads by opening or closing of the gas passage aperture is another principle drawback.
Investigations have demonstrated that the valves which are mounted for covering the gas aperture of a material exchanger bottom, can adapt only incompletely to the changing gas loads. With partial loads, it is by no means the case that all valves of the bottom adapt by partial opening to the low gas load and even remain in this position. Rather, all the gas passage openings of the bottom remain closed under partial load by the valve covers until the pressure of the gas beneath the bottom has risen so far that suddenly part of the bottom apertures will be released by lifting of the valve covers. These valve covers open as far as the maximum stop and then they also remain in this maximum opening position. However, commensurate with the partial load of the gas the opened gas passage openings only represent part of the total openings present in the bottom. True, in this bottom part the liquid will be attacked by the gas and thus an exchange of material will come to pass, however, only very incompletely, for simultaneously with the opening of part of the gas passage opening on the bottom and passage of the entire gas current available, the gas pressure prevailing beneath the remaining gas passage openings is eliminated, although the related openings are covered by valve plates. Because for corrosion and hydraulic reasons the valve plates never shall nor can seal the gas passage openings in the bottom completely, the liquid flowing there above the bottom dribbles off, so that soon the bottom will run idly and thus the entire column will reach the point of failure.
Consequently, the invention is based on the problem of creating an exchanger element for material exchanger bottoms which to a large extent adapts to the changing gas loads without the gasification of the fluid and thus improving the degree of bottom effectiveness.